1. Field of the Invention
The present invention generally relates to optical stacked structure inspecting methods and optical stacked structure inspecting apparatuses, and more particularly to an optical stacked structure inspecting method and an optical stacked structure inspecting apparatus for inspecting a dye layer thickness and/or a dielectric layer thickness of an optical stacked structure in which a reflection layer and an organic dye layer are successively stacked on a substrate or, a reflection layer, an organic dye layer and a dielectric layer are successively stacked on a substrate. The present invention also relates to a method and an apparatus for producing such an optical stacked structure.
2. Description of the Related Art
Generally known write-once type optical recording media, to which information can be written once by a laser beam, include CD-R, DVD+R and DVD-R. Such write-once type optical recording media have a stacked structure made up of a transparent polycarbonate substrate formed with a tracking groove, a recording layer made of an organic dye spin-coated on the substrate, a light reflection layer made of Au or Ag sputtered on the recording layer, and a projection layer made of an ultraviolet curing resin that are stacked in this order. The DVD+R and the DVD-R have a structure in which two substrates having a thickness of 0.6 mm are bonded together, and have a large recording capacity.
As a method of inspecting the layer thickness of the organic dye recording layer during the production process of the write-once type optical recording medium, a Japanese Laid-Open Patent Application No. 2002-510107 proposes a method of measuring the layer thickness based on transmitted or reflected light that is diffracted by the groove.
A Japanese Laid-Open Patent Application No. 2002-367244 proposes a method of measuring the thicknesses of a land part and a groove part based on diffracted light of different orders, and inspecting the dye layer thickness by measuring the transmittance and the diffracted light intensity in a state where the dye layer is formed on the substrate.
In addition, a Japanese Laid-Open Patent Application No. 11-66633 proposes an apparatus for inspecting defects from the reflected light using, as the inspection light, light having a characteristic absorption wavelength of the dye as a main component.
The existing DVD-ROMs for read use include those having two information recording layers for the purpose of increasing the recording capacity. A first substrate and a second substrate are bonded via a transparent intermediate layer made of an ultraviolet curing resin. A first information recording layer L0 has a semi-transparent first layer formed on an inner surface of the first substrate formed with concavo-convex pits. A second information recording layer L1 has the transparent intermediate layer and a metal reflecting second layer formed on the first information recording layer L0. The semi-transparent first layer is formed by a dielectric layer or a thin metal layer.
By converging a reproducing laser beam on the first information recording layer L0 or the second information recording layer L1 and detecting the reflected light therefrom, it is possible to reproduce the signal from the corresponding first information recording layer L0 or second information recording layer L1. Since the signals are read from the two information recording layers L0 and L1, it is possible to obtain a maximum recording capacity of approximately 8.5 GB.
Recently, a type of optical recording medium having two recording layers and having information reproducing compatibility with the DVD-ROM having the first and second information recording layers L0 and L1 has been developed. This type of optical recording medium is made up of a first substrate and a second substrate that are bonded via an adhesive agent. The first substrate includes a transparent substrate formed with a groove, a recording layer made of an organic dye formed on the substrate, a semi-transparent reflection layer formed on the recording layer, and an ultraviolet curing resin formed on the recording layer, that are stacked in this order. The second substrate includes a substrate formed with a groove, a total reflection layer formed on the substrate, a recording layer made of an organic dye formed on the substrate, and a transparent organic thin film formed on the recording layer, that are stacked in this order. Examples of this type of optical recording media are proposed in Japanese Laid-Open Patent Applications No. 10-340483 and No. 2000-311384.
However, when producing this type of optical recording medium by forming the recording layer and the semi-transparent reflection layer on each substrate and bonding the first and second substrates, there was a problem in that the thicknesses of the dye layer formed on the total reflection layer and the dielectric layer formed on the dye layer cannot be measured using the transmitted light because the light cannot be transmitted through the total reflection layer of the second substrate.